This invention relates to an improved engine block casting and crankshaft bearing assembly, and in particular relates to an arrangement of a cast engine block and crankshaft bearing assembly that simplifies casting of the engine block and enables seating of the crankshaft in a bearing assembly that has means for minimizing vibrations transmitted between the crankshaft and the engine block. In addition to simplifying the engine block casting, the improved construction provides for a lighter weight assembly that is less expensive to fabricate.
In casting prior art engine blocks, the support structure for the crankshaft bearings has typically included a web divider in the crankcase structure below the engine cylinders. The cast divider included the upper bearing cap integrally formed into the divider structure. Bearing shells are installed in an upper crescent of the upper bearing cap and in a removable lower bearing cap which is secured to the upper bearing cap by a pair of spaced bolts. Locating a cast divider between each of a plurality of cylinders complicates the structure of the engine block and adds to its expense and weight.
Since the thrust of the pistons is directed to the crank pins of the rotating crankshaft, the main forces of piston thrust are transmitted to the lower bearing cap and to the engine block casting via the cap bolts. Forces on the shell of the upper bearing cap that encases the bearing sleeve are not as extensive and, therefore, materials other than rigid cast materials can be utilized to advantage. Although high strength, forged steel parts can be fabricated with minimum material for lightness of weight, such parts have traditionally not been used for bearing caps for the crankshaft.
It is a primary object of this invention to utilize a forged steel upper bearing cap in a cast engine block to simplify the casting of the block. In addition, the use of a formed bearing cap enables the composition and structure to be optimized for the particular operating conditions encountered. It is a further object of this invention to incorporate the forged bearing cap in an assembly that includes a vibration damping material to insulate the engine block from vibrations imparted to the crankshaft by the connected piston and connecting rod assemblies. The engine block casting and crankshaft bearing assembly of this invention is particularly useful for automotive type engines where costs, fabrication procedures or other factors make the use of a removable upper bearing cap advantageous.